TweetFollow Us on Twitter

Aug 98 Tips

Volume Number: 14 (1998)
Issue Number: 8
Column Tag: Tips & Tidbits

August 1998 Tips

by Steve Sisak, tips@mactech.com

Gotcha - Calling GetResource()

If you call Get1Resource(), expecting to get a resource from the topmost resource file, you can be unpleasantly surprised. With the introduction of the "Fonts" folder in System 7.1, a patch was made to the resource manager so that all the files in the fonts folder will appear to be part of the System file, even though they are not.

Most of the time this is not a problem, since most people don't care if a resource is in the System file or in a file in the fonts folder (or in the enabler, or in ROM).

However, if you absolutely need to know the file where a resource is loading from, you can use HomeResFile(). It will return the refNum of the resource file the resource came from.

Marshall Clow, Adobe Systems


Determining if a Resource File was Actually Opened

When you use any of the Resource Manager calls for opening a resource file, and the resource file is already open by the Resource Manager with that access, it will not open the file again. Instead, it returns the refNum of the already-open reference, and also does the equivalent of a UseResFile() on that refNum.

This means you have to be careful if your code is capable of opening and closing arbitrary resource files - if the Resource Manager didn't actually open the file for you (for example if you were to open your own application, or the System file, or a suitcase in the Fonts folder), then you must not close it with CloseResFile().

So how do you tell if the resource file was actually opened for you or not?

It's easy: if the resource file was opened, then its resource map will be added to the top of the in-memory chain of resource maps (pointed to by the "TopMapHndl" low-memory global). If not, then the chain remains unchanged.

The following sequence illustrates the idea:

  SInt16    TheResFile, PreviousResFile;
  Boolean   ReallyOpened;
  Handle    PreviousTop;

  PreviousResFile = CurResFile();
  PreviousTop = LMGetTopMapHndl();
  TheResFile = FSpOpenResFile(ResFileSpec, Permissions);

/* checking for errors omitted */

  ReallyOpened = LMGetTopMapHndl() != PreviousTop;

/* do your processing on the resources, then when finished, restore things as they were: */

  if (ReallyOpened)
    CloseResFile(TheResFile);
  UseResFile(PreviousResFile);

Lawrence D'Oliveiro, Hamilton, New Zealand


Serial Port Tidbits Comments

Thanks for the informative article bringing together a lot of previously hard to find information. I spent many hours digging around (and cursing!) trying to find that same info.

I had written a similar routine to your FindPortInfo() routine, and after checking mine, I initially thought there might be a bug in yours. I finally realized that your code was in fact right, but there is a subtlety which might not be apparent to readers.

In the line:

while ((crm = CRMSearch(crm)) != nil)

a key point is that you are reassigning to crm the result of the search. In my code I was using a temporary variable to pass to CRMSearch(), as in

while ((foundCRM = CRMSearch(tempCRM)) != nil)

This means that in my code, after the EqualString() check, I need to insert:

tempCRM->crmDeviceID = foundCRM->crmDeviceID;

to avoid a potential infinite loop.

Your code (and the code in the CTB book) avoids this by using the same variable in the assignment, but that also hides this subtle point CRMSearch() starts looking from the device ID passed to it in the crmDeviceID field of the CRMRecPtr passed to it.

One other thing I'd like to mention is that instead of your IsDriverOpen() routine, you could call the Connection Resource Manager routine CRMIsDriverOpen(), described in the Communications Toolbox 1.1 Engineering Notes (not in the original CTB book - the 1.1 notes are another hard-to-find source...)

Jim Wintermyre, E-mu Systems, Inc.

Ed Note: The fact that CRMSearch() looks at the deviceID and deviceType passed in and returns the device of the same type with the next higher ID. This is a subtlety worth noting. Also, the CTB 1.1 Engineering Notes are an important resource I forgot to mention in the original article.
-sgs

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Whitethorn Games combines two completely...
If you have ever gone fishing then you know that it is a lesson in patience, sitting around waiting for a bite that may never come. Well, that's because you have been doing it wrong, since as Whitehorn Games now demonstrates in new release Skate... | Read more »
Call of Duty Warzone is a Waiting Simula...
It's always fun when a splashy multiplayer game comes to mobile because they are few and far between, so I was excited to see the notification about Call of Duty: Warzone Mobile (finally) launching last week and wanted to try it out. As someone who... | Read more »
Albion Online introduces some massive ne...
Sandbox Interactive has announced an upcoming update to its flagship MMORPG Albion Online, containing massive updates to its existing guild Vs guild systems. Someone clearly rewatched the Helms Deep battle in Lord of the Rings and spent the next... | Read more »
Chucklefish announces launch date of the...
Chucklefish, the indie London-based team we probably all know from developing Terraria or their stint publishing Stardew Valley, has revealed the mobile release date for roguelike deck-builder Wildfrost. Developed by Gaziter and Deadpan Games, the... | Read more »
Netmarble opens pre-registration for act...
It has been close to three years since Netmarble announced they would be adapting the smash series Solo Leveling into a video game, and at last, they have announced the opening of pre-orders for Solo Leveling: Arise. [Read more] | Read more »
PUBG Mobile celebrates sixth anniversary...
For the past six years, PUBG Mobile has been one of the most popular shooters you can play in the palm of your hand, and Krafton is celebrating this milestone and many years of ups by teaming up with hit music man JVKE to create a special song for... | Read more »
ASTRA: Knights of Veda refuse to pump th...
In perhaps the most recent example of being incredibly eager, ASTRA: Knights of Veda has dropped its second collaboration with South Korean boyband Seventeen, named so as it consists of exactly thirteen members and a video collaboration with Lee... | Read more »
Collect all your cats and caterpillars a...
If you are growing tired of trying to build a town with your phone by using it as a tiny, ineffectual shover then fear no longer, as Independent Arts Software has announced the upcoming release of Construction Simulator 4, from the critically... | Read more »
Backbone complete its lineup of 2nd Gene...
With all the ports of big AAA games that have been coming to mobile, it is becoming more convenient than ever to own a good controller, and to help with this Backbone has announced the completion of their 2nd generation product lineup with their... | Read more »
Zenless Zone Zero opens entries for its...
miHoYo, aka HoYoverse, has become such a big name in mobile gaming that it's hard to believe that arguably their flagship title, Genshin Impact, is only three and a half years old. Now, they continue the road to the next title in their world, with... | Read more »

Price Scanner via MacPrices.net

B&H has Apple’s 13-inch M2 MacBook Airs o...
B&H Photo has 13″ MacBook Airs with M2 CPUs and 256GB of storage in stock and on sale for up to $150 off Apple’s new MSRP, starting at only $849. Free 1-2 day delivery is available to most US... Read more
M2 Mac minis on sale for $100-$200 off MSRP,...
B&H Photo has Apple’s M2-powered Mac minis back in stock and on sale today for $100-$200 off MSRP. Free 1-2 day shipping is available for most US addresses: – Mac mini M2/256GB SSD: $499, save $... Read more
Mac Studios with M2 Max and M2 Ultra CPUs on...
B&H Photo has standard-configuration Mac Studios with Apple’s M2 Max & Ultra CPUs in stock today and on Easter sale for $200 off MSRP. Their prices are the lowest available for these models... Read more
Deal Alert! B&H Photo has Apple’s 14-inch...
B&H Photo has new Gray and Black 14″ M3, M3 Pro, and M3 Max MacBook Pros on sale for $200-$300 off MSRP, starting at only $1399. B&H offers free 1-2 day delivery to most US addresses: – 14″ 8... Read more
Department Of Justice Sets Sights On Apple In...
NEWS – The ball has finally dropped on the big Apple. The ball (metaphorically speaking) — an antitrust lawsuit filed in the U.S. on March 21 by the Department of Justice (DOJ) — came down following... Read more
New 13-inch M3 MacBook Air on sale for $999,...
Amazon has Apple’s new 13″ M3 MacBook Air on sale for $100 off MSRP for the first time, now just $999 shipped. Shipping is free: – 13″ MacBook Air (8GB RAM/256GB SSD/Space Gray): $999 $100 off MSRP... Read more
Amazon has Apple’s 9th-generation WiFi iPads...
Amazon has Apple’s 9th generation 10.2″ WiFi iPads on sale for $80-$100 off MSRP, starting only $249. Their prices are the lowest available for new iPads anywhere: – 10″ 64GB WiFi iPad (Space Gray or... Read more
Discounted 14-inch M3 MacBook Pros with 16GB...
Apple retailer Expercom has 14″ MacBook Pros with M3 CPUs and 16GB of standard memory discounted by up to $120 off Apple’s MSRP: – 14″ M3 MacBook Pro (16GB RAM/256GB SSD): $1691.06 $108 off MSRP – 14... Read more
Clearance 15-inch M2 MacBook Airs on sale for...
B&H Photo has Apple’s 15″ MacBook Airs with M2 CPUs (8GB RAM/256GB SSD) in stock today and on clearance sale for $999 in all four colors. Free 1-2 delivery is available to most US addresses.... Read more
Clearance 13-inch M1 MacBook Airs drop to onl...
B&H has Apple’s base 13″ M1 MacBook Air (Space Gray, Silver, & Gold) in stock and on clearance sale today for $300 off MSRP, only $699. Free 1-2 day shipping is available to most addresses in... Read more

Jobs Board

Medical Assistant - Surgical Oncology- *Apple...
Medical Assistant - Surgical Oncology- Apple Hill Location: WellSpan Medical Group, York, PA Schedule: Full Time Sign-On Bonus Eligible Remote/Hybrid Regular Apply Read more
Omnichannel Associate - *Apple* Blossom Mal...
Omnichannel Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Cashier - *Apple* Blossom Mall - JCPenney (...
Cashier - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Blossom Mall Read more
Operations Associate - *Apple* Blossom Mall...
Operations Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Business Analyst | *Apple* Pay - Banco Popu...
Business Analyst | Apple PayApply now " Apply now + Apply Now + Start applying with LinkedIn Start + Please wait Date:Mar 19, 2024 Location: San Juan-Cupey, PR Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.